Revealing the hidden world of the small spotted catshark (Scyliorhinus canicula): investigating behaviour and spatial ecology using acoustic telemetry

2. November 2023

Feauture photo by: David Villegas-Rìos
In a recent study, scientists from Instituto de Investigaciones Marinas, CSIC, Spain, investigated the spatial ecology of the small spotted catshark using acoustic telemetry. The study took place at the Cìes Islands, located north-west off the coast of the Iberian Peninsula.
The findings revealed substantial variations in spatial behaviour influenced significantly by both living (biotic) and non-living (abiotic) factors at different timescales.
Beneath the ocean’s surface lies a hidden world of wonder, where the small-spotted catshark (Scyliorhinus canicula) makes its home along the seabed. You can find this species in the northeastern Atlantic and Mediterranean coastal areas. These small sharks are often at risk of getting accidentally caught by fishermen as by-catch. A more detailed study of their spatial and temporal behaviour could provide valuable insights into enhancing their protection through proper management and the creation and development of Marine Protected Areas (MPAs).

Photo by: David Villegas-Rìos
Shark movements recorded with implanted D-LP9L Thelma Biotel acoustic transmitters
Among the individuals in the study, six small-spotted catsharks were tagged with Thelma Biotel D-LP9L (Depth sensor) transmitters to track the movement and depth of the sharks. Our transmitters, when equipped with an additional battery package (L), provide significantly longer battery life, allowing you to collect more data from your study species. The data from the Thelma Biotel transmitters were also processed through our PinPoint positioning service to achieve high-resolution spatial positioning of the tagged sharks.

Photo by: Kenn Papadopoulo

Female sharks exhibited a higher residency in the study area
The study showed that tagged female sharks were more likely to remain in the study area than the males. These findings raise the question of whether a part of the small-spotted catshark population in the area is mainly sedentary. In contrast, the range of the total population is believed to exceed that of the study area and the MPA.
Higher activity during nighttime
Significantly higher activity was observed in the tagged small-spotted catsharks at night. They appeared to move more and cover a larger area during nighttime, indicating a clear diel split in their activity.
Additionally, there was a size-related difference in activity, with larger individuals being less active than the smaller ones. The sharks in the study also showed increased activity with rising temperatures up to 17 degrees Celsius, after which a decline was observed with further warming of the waters.

Photo by: David Villegas-Rìos
There’s no doubt that the wonderful small-spotted catshark species plays a vital role in the ecosystems it inhabits. Therefore, it’s crucial to continue building upon the scientific data to develop effective conservation measures for their protection. By studying and understanding the behaviour of these sharks at various life stages, we can work toward reducing the significant by-catch and use this knowledge to make informed decisions within fisheries and conservation.
MPAs play a crucial role in the worldwide conservation of aquatic species. However, they typically provide more protection to sedentary species than those covering larger areas, such as many shark species. Ideally, MPAs should be designed to accommodate the biology of the species they aim to protect throughout various life stages and sexes.
Key findings from the study, essential to consider for conservation measures, reveal that while the MPA in the area may not have been explicitly designed to protect the small-spotted catshark, it could provide refuge for more sedentary individuals in the region. Nonetheless, future studies should explore additional habitats crucial for the shark species and aim to protect them. This includes expanding the acoustic telemetry array to cover more coastal waters due to the study populations’ higher connection compared to the more open ocean.
Higher nighttime activity observed in the study is also a factor to consider when discussing conservation measures. Implementing restrictions during peak activity times could reduce heavy catches of the shark species as bycatch if applied thoughtfully.
Understanding the spatial behaviour of aquatic animals, especially shark species, presents a significant challenge. However, this knowledge is vital for developing effective strategies to protect these species in the future. The small-spotted catshark is just one of many species being investigated using acoustic telemetry technology. Questions that were once hidden in the world of aquatic animals are now accessible with suitable acoustic telemetry equipment.
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